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Paris airport: 'Weak points'

PARIS — A commission investigating the partial collapse last May of an ultramodern terminal at France's main international airport reported its findings Tuesday, placing the blame on "weak points" in the building's complex design.

Jean Berthier, a senior French engineer who led the panel, cited a number of construction weaknesses that left the arched concrete roof of the terminal at Roissy-Charles de Gaulle International Airport near Paris vulnerable to changes in exterior temperature. The temperature swings caused the material to expand and contract, and eventually crumble, he said.

It remained unclear whether the wing where the accident occurred would have to be razed and rebuilt, or whether it could be restored. "My judgment is that everything is savable," Berthier said. "Even with very old buildings, we should always try to save them first. The real problem is one of price."

Four people were killed when a 30-meter, or 100-foot, glass-and-steel section of the airport's Terminal 2E collapsed on May 23. The sleek, Â750 million, or $975 million, terminal had been in service for less than a year.

The panel did not assign blame among designers or contractors. Berthier emphasized that the mandate of his commission was limited to determining the technical failures at the root of the accident.

He also stressed that the mandate, unlike a parallel judicial investigation, was not to identify those responsible.

Berthier argued that the section that collapsed had contained several structural weaknesses, including the fact that concrete beams holding up the roof were pierced by ventilation shafts every four meters. He also cited the fact that passenger bridges to the terminal were asymmetrical.

Berthier said he also suspected a lack of steel reinforcement in the concrete, but had been unable to verify this because his commission had not been given access to the site pending the conclusion of the separate judicial investigation, which is still ongoing.

He said that the day of the accident had been the coolest that month.

"The most probable scenario for us is that these temperature cycles progressively weakened the structure," Berthier said. He said that the inside of the roof shell was air-conditioned, keeping the interior temperature stable, but that outside variations in temperature - even between day and night - had caused the concrete to "breathe." The rooftop consequently moved as much as 2 centimeters, or nearly 0.8 inches, leading to a gradual deformation of the roof.

In time, the concrete of the weakened roof was pierced by exterior steel struts, he said. In addition, a horizontal concrete beam holding up the roof on the southern side of the terminal appeared to have slipped out of its base, Berthier said. "It therefore seems that, instead of one cause of collapse, we should speak of a combination of events that took place," said the panel's report, which was commissioned last year by Transport Minister Gilles de Robien.

Berthier said that faults in the actual concrete or steel used in the construction could be ruled out as a main cause of the accident, as could a collapse of the pillars holding up the roof.

"The form is complicated, it doesn't lend itself easily to calculations," Berthier said. A key recommendation of the report was that complex buildings like Terminal 2E should be subjected to a second, independent, computer-generated calculation.

Pierre Graff, head of the state-owned airport operator, Aéroports de Paris, said last week that he would decide in two months whether to raze Terminal 2E. Either way, analysts say, the terminal will not reopen before 2007.

The report on Tuesday steered clear of apportioning blame, limiting its conclusions to the technical failure at the root of the collapse. But it will help inform the judicial investigation, which aims to determine whether the accident was the fault of the terminal's architects or its builders. Those considered responsible could find themselves in court for homicide and accidental injury.

After parts of the Berthier report were leaked to the French press last week, Paul Andreu, the architect of Terminal 2E, released a statement saying that "the degree of reinforcement is not a problem of conception and of the competence of the architect but it constitutes an executive task" that belongs to the construction companies.

On the construction side, GTM, a subsidiary of the French construction giant Vinci, was responsible for building the terminal. Veritas, another French company, was in charge of verifying the calculations the engineers undertook and on which they based their work. Aéroports de Paris carried the title of lead engineer and project manager throughout the construction period.